A trial aimed to evaluate the efficacy of Deltamethrin (0.4% impregnated odour-baited targets and 1% pour-on formulation applied to animals) in reducing the incidence of bovine trypanosomosis and comparing the corresponding cost-effectiveness of both strategies was conducted in two selected 10X10km Universal Transverse Mercator Grids of the Southern Tsetse Eradication Project (STEP) area in the Southern Rift Valley of Ethiopia. The Grids selected were H3 & G5 designated as study Sites I & II respectively. The trial was underway from late September, 2003 to early April, 2004. The accomplishment of the trial included baseline survey (Questionnaire, Parasitology, and entomology), intervention with insecticide (Deltamethrin 0.4%) impregnated odour-baited targets at Site I(Grid H3) and Deltamethrin 1% â€˜pour-onâ€™ application to cattle at Site II (Grid G5) and monthly monitoring of the incidence of disease and apparent density of tsetse fly. Following the deployment of 460 targets (0.4% Deltamethrin impregnated and odour-baited) at a density of 4 targets /km2 at the trial Site I, the relative abundance of tsetse fly (G. pallidipes) population declined from a pre-intervention catch of 1.35 flies/trap/day to 0.05 flies/trap/day during the final trapping time in April, 2004 with about 88.88% overall reduction achieved. The associated disease (trypanosomosis) status was monitored by monthly blood sampling from the sentinel animals established prior to the intervention and the incidence in cattle dropped from 10.75% (first monitoring) to 1.8% (last monitoring) with about 83.25%. The prevalence of the disease had also dropped to 9% (P< 0.01) as compared to the pre-intervention result of 23% and as a result, an overall reduction of 60% was achieved. The corresponding overall mean PCV (packed cell volume) record had shown an improvement from 21.8% of the pre-intervention to 25.5 % (P